1. Field of the Invention
The present invention relates to creping adhesives and more particularly it relates to creping adhesive obtained by reacting polyamide and polyvinylalcohol with epichlorohydrin.
2. Description of the Prior Art
The creping process is commonly practiced in the manufacture of tissue and towel grades of paper. This process involves scraping the dried paper web from a drying cylinder (Yankee dryer) by the use of a creping doctor blade. The creping action imparts a fine, rippled texture to the sheet and also increases the bulk of the sheet, resulting in improved softness and absorbency. An adhesive formulation is often used to control the adherence of the paper sheet to the Yankee dryer. In this regard, fibrous webs, particularly paper webs, are conventionally subjected to the creping process in order to give them desirable textural characteristics, such as softness and bulk. The creping process typically involves applying creping adhesive-generally in the form of an aqueous solution or dispersion--to a drying surface for the web; preferably, this surface is the surface of a rotating creping cylinder, such as the apparatus known as a Yankee dryer. The web is then adhered to the indicated surface. It is subsequently dislodged from the surface with a creping device--preferably, a doctor blade. The impact of the web against the creping device ruptures some of the fiber-to-fiber bonds within the web, causing the web to wrinkle or pucker. The creping adhesive solution or dispersion can comprise one or more adhesive components, typically water-soluble polymers, and may also contain one or more release agent components as well as any other desired additives that may affect the creping process. This is known as the creping adhesive package.
U.S. Pat. No. 3,224,986 discloses a process for preparing a water-insoluble resin which comprises reacting a polyalkylene polyamine with a saturated dicarboxylic acid to produce a polyamide, then reacting the polyamide with epichlorohydrin at an epihalohydrin:polyamide mole ratio of from 0.5:1 to 8:1 adjusting the pH and reacting the resin with a water soluble polymer selected from a group which includes polyvinylalcohol having a degree of hydrolysis of 77%.
U.S. Pat. Nos. 4,501,640, 4,528,316, 4,684,439, and 4,788,243 disclose cellulosic webs creped with a creping adhesive consisting of polyvinylalcohol of molecular weight 90,000-140,000 and degree of hydrolysis of 80-90% and a polyamide-epicholorohydrin resin. The ratio of epi to secondary amide groups in the polyamide is from 0.5:1 to 8:1.